The above type of conveyor belt is advantageous for inter alia air treatment of food products in cooling, freezing or cooking the food products. The conveyor belt is often made to follow a helical path forming a stack of helically wound tiers.
Each belt element is movable relative to adjoining belt elements about two axes perpendicular to the longitudinal direction of the belt and situated one in the plane of the belt and the other perpendicular thereto.
In order to make as full use as possible of the volume taken up by the stack, the inner radius of the helical path in the stack should be small. However, this requires a substantial collapsing of the corresponding inner side of the belt when transferring from a straight path to a helical path, thereby reducing the area of the belt in its straight stat that can be used in the curved state of the conveyor belt, unless the outer side is expanded at the same time as the inner side is collapsed.
U.S. Pat. No. 4,075,655 discloses a conveyor belt having a plurality of rods extending across the belt and pivotally connected by links at the inner and outer edges of the belt. The belt also has a row of central tractive links controlling the simultaneous collapsing of the inner side of the belt and expanding the outer side of the belt. However, these central links must be rigidly secured to the transverse rods, e.g. by welding, so as to not shift their position laterally. Also, the links project above the load-carrying surface of the belt such that it is not as smooth as desired.
WO 98/09893 discloses a conveyor belt having a plurality of rods and a plurality of side members at both lateral edges of the belt connected in pairs by the rods. A wire netting is supported by the rods and comprises a plurality of wires. A separate one of said wires forms a joint intermediate the lateral edges of the belt between each pair of adjoining rods, each transverse rod in said pair connecting a separate pair of side members such that the joint takes up tractive forces at least along straight parts of the conveyor belt path. The joints need not be rigidly secured to the rods and do not project from the load-carrying surface of the belt. However, in certain cases the joint may break due to high level stress exposure resulting in a conveyor belt breakdown.
Consequently, there is a need of a conveyor belt which also in case of high level stress exposure has a high reliability in operation.